Vacuum switch



C. T. ULREY VACUUM SWITCH Oct. 3, 1933.

Filed March 2.9, 1932 patentedv y Oct. 3, 14933 UNITED STATES 1,929,155 l VACUUM SWITCH Clayton Tridle Ulrey, East Orange, N. J., assignor l to Westinghouse Lamp Company, a corporation of Pennsylvania Applcaton'March 29, 1932. Serial No. 601,865

8 Claims. (Cl. 200-144) This invention is directed to an electrical switch and more particularly to a switch of the vacuum type for accomplishing the make and break of an electrical circuit. In its more specific aspect the invention particularly relates to a rugged switch adapted to close a high potential circuitwithout excessive arcing and Without causing appreciably high voltage surges in an electrical circuit.

In the production of radiographs, and especially those of the X-ray type, it has heretofore been found essential that in order that these radiographic X-ray films may embody sharp shadow images, the time of exposure or the time of subjecting the body to be X-rayed to an X-ray beam should be of comparatively short duration.

In this particular art, circuits employing an X-ray tube in series with a switching or interrupting means have been utilized in the production of what is-known in the X-ray art as short exposure radiographic films. The switching or interrupting means heretofore proposed for use in circuits of this character include among others the ordinaryair gap, timing switches and the like.- Although these switches and interrupters have found utility in discharging condensers connected in series therewith and with an X-ray tube, they have not'been complete solutions of the switching problem because of the' patient frightening arcingnoises, power consumption and/or other deficiencies generally incident thereto.

In order that I might overcome these difliculties andk so as to provide a switch of relative high efficiencies and sundry adaptabilities I have designed the vacuum switch hereinafter more fully described. This switch may be effectively employed in the X-ray circuit disclosed in the application of. N. C. Beese, Serial No. 584,327 filed January 2, 1932.

Brieiiy stated, my invention comprises a simple, .compact vacuum switch including an envelope having a plurality of re-entrant tubes, a stationary electrode supported by one of said tubes, a relatively 'movable electrode guided by another re-entrant tube and a magnetic Vwinding located outside oi' said envelope and adapted to actuate said movable electrode.` An object of my invention is to provide a relatively simple, inexpensive vacuum switch of relatively light weight adapted to close an electric circuit without causing high voltage surges therein or exhibiting excessive arcing between the electrodes.

` Another object of my invention is to provide a vacuum switch of simple and economical design for closing an X-ray circuit `without the'danger of excessive deleterious discharges within the device or seal fracture.

Another object of my invention is to provide a 00 K relatively inexpensive vacuum switch which is of relatively lightweight and small size so that when it is combined with other elements of an X-ray apparatus, it will not necessitate heavy and cumbersome frames and supporting standards.

Another object of my invention is to provide 'a switch adapted to complete an electrical circuit to allow the instantaneous passage therethrough of high potential and high current X-ray values without excessive arcing.

Other objects and advantages oi'4 my invention will become readily apparent from the following specification and appended drawing wherein;

Figure 1 represents a longitudinal cross sectional view with some of the parts in elevation of a vacuum switch embodying my invention;

Figure 2 represents a fragmentary longitudinal cross sectional view with some of the parts in elevation of a vacuum switch embodying my invention and is a modification of Figure 1. so One embodiment of my invention, as illustrated injFig'ure 1, comprises a dielectric envelope 10 consisting of a bulbous mid-portion 11, and tubular arms 12 and 13. Extending into said tubular arm 13v is a re-entrant tube 14 of smaller outside diameter than the corresponding internal dimension of said tubular army and having. its outer wall spaced from the inner wall thereof. At the upper end of said reentrant tube 14 is a vitreous press 15in which is sealed a rigid leading-in and supporting wire 16, composed of molybdenum or the like. This rigid leading-in and supporting wire 16 has a portion thereof extending` within the envelope, a portion thereof forming an air tight seal with the vitreous press 15 and another portion thereof extending outside of said press and beyond the limit of said envelope.

Over the outer limit of said` support wire 16, spaced around and secured to the outer limit of the tubular arm 13 is secured a metallic cap 1'7 electrically connected to said supporting wire 16. Surrounding a portion of the reentrant stem 14, the press 15 and that portion ofthe supporting wire 16 within the envelope, is a tubular molybdenum shell 18. The shell 18 has spring fingers 19 secured to the inner wall thereof to engage frictionally the outer wall of said reentrant stem 14. for the purposes hereinafter described.

Attached to the upper end oi' said lead-in wire 16 and. having the outer wall thereof in contact no with the upper portion of the inner wall of said tubular section 18 is a molybdenum cup 20. A contact element 21 is rigidly secured to said tubular section 18 by a mechanical means,v such 5 as rivets or the like. The contact element 21 comprises essentially a tubular section flared f smoothly outwardly in a direction away from the upper end of the tubular section 18, with its upper end being in the form of a curled lip of d lo substantial radius-having its free edge located below the plane of curl and in a plane substantially normal to the longitudinally axis of the tube. By virtue of this construction the smooth faced contact 21 is free from sharp points and lines to prevent the establishment of relatively high potential gradients along the surface thereof during 'certain periods of switch operation to minimize the danger of cold electron emission.

At the other end of the envelope and at the end of the tubular arm l2 is a relatively short reentrant tube composed of glass, the same material as the envelope 10 and the reentrant tube 14. This reentrant stem 25 has a press 26 which forms an air-tight seal with a rigid 25 support and lead-in wire 27 having a portion thereof extending within the tube andv another portion thereof extending exteriorly of the tube. Housing the exterior portion of said support and lead-in wire 27 and the extremity of said tubular 30 arm 14 is a contact cap 28 secured thereto.

Intermediate said press 26 and said bulhous portion 11 is another reentrant tube 30 having its outer edge fusedly ring-sealed to the inner wall of said tubular section at a position of about they mid-length of tubular arm 12.

Said re-entrant tube 30 has a cylindrical body portion 31 of appropriate length, preferably the same as that of the tubular section 12, extending towards the contact 20. The internal diameter of this dielectric guide A30 is of any appropriate dimension and preferably of such a magnitude as to accommodate a relatively movable con tact 32.

|I'he body of the relatively movable contact 32 consists essentially of a tubular shell 33 whose external diameterV is preferably slightly less than the corresponding internal dimension of guide 30. Secured to the lower end oi' said tubu-= lar' sleeve 33 is an enlarged molybdenum cup or thimble 34 with the open end of said thimble or cup surrounding the lower portion of said tubular sleeve and with the upper edge of said thimble being disposed in a direction away from the contact 21.

Into the upper end of said tubular sleeve 33 is a closely fitting soft iron cylinder 35 having an opening 37 extending throughout the length thereof to provide a means whereby the gases within said movable member may nd egress therefrom during that period in which the tube is evacuated. Intermediate that portion of the rigid lead-in and support wire 27 and the upper lend of said cylindrical soft iron block 35 is a compression spring 36 having one end thereof secured to the upper surface of said block 35 and its other lend secured to the support wire 27. This compression spring has distinct and separate functions; -rst, it serves as a flexible electrical conducting means between the lead-in wire 27 andthev movable electrode 32; secondly, it acts as a cushioning means on the breakto prevent seal fracture at the upper end of the envelope.

Exteriorly of. ysaid envelope and surrounding the same at about the mid-length of the tubular section 12 is a magnetic winding 40 which upon -length that the contact cups 17 and 28 are Lasarte i energization is adapted to actuate the movable electrode in a directionaway from the contact 21. Upon de-energization thereof. this movable electrode, because of its mass and due to gravity, will travel towards and finally have the outer surface of -its thimble or contact portion 34 ride into the outwardly flared contact portion 21 of the stationary electrode to make a good .surface contact therewith. l

In this construction the tube is of such a spaced from each other a sufficient distance to prevent spark-over therebetween in its ambient medium when a relatively high voltage as for exampleforty thousand volts or upwardly is applied therebetween. The envelope 10 is preferably highly evacuated and because the contacts are of rounded configuration and contain no sharp edges or points, the contacts within the tube need be separated only a short distance Without any danger of cold electron emission. Moreover, the particular construction of the stationary electrode and; especially the shell 18 takes up some of the strain during contact to relieve and protect the seal at 15.

Another embodiment of my invention, illustrated in Figure 2, is the same as that illustrated in Figure 1 and hereinbefore described except for the relatively movable electrode. In place of the relatively movable electrode disclosed in Figure 1, I may employ a relatively movable electrode 50 illustrated in Figure 2.

This movable electrode 50 comprises essentially an elongated tubular shell 51, a cup 52, a thimble 53, a supporting rod 54 and an annular 110 soft iron ring 55. The elongated tubular shell 5l consists essentially of a relatively thin molybdenum tubular section having an internal diameter slightly greater than the corresponding external dimension of the dielectric guide 30.

ASecured to the lower end of said tubular section 51 is the molybdenum cup 52 perforated as at 56. Depending from and surrounding the lower end of said tubular section 51 with its upper edge located in a direction away from the stationary contact is the enlarged molybdenum thimble 53, -which serves to make a relatively large surface area contact with the stationary contact 21. The annular soft iron ring 55 has its inner periphery surrounding the upper end of the tubular section 51 and is appropriately secured thereto by mechanical means, such as angle irons 57.

Between the lower end of tri compression spring 36 and the cup 52, is a rigid molybdenum supporting rod 54 having its lower end secured to the base of the cup 52 and at its upper end secured to the lower end of the compression spring 36. This movable electrode is actuated in the same manner as the movable electrode illustrated in Figure 1 and differs from the movable electrode illustrated in Figure l only in that the reentrant tube 30 is located within this movable electrode whereas in Figure l the guide ds located exteriorly of the movable electrode.

In order that tubes of this character may be efilciently employed as a means for breaking" and eillciently. making an electrical circuit of relatively high voltage, it is essential that no appreciable gas ionization take place to cause 145 power losses while the apparatus is in operation. Thus, a conditioning'of the interior of the tube is necessary so as to provide a relatively high vacuum which may be of the order of about 10l to 10 millieters of mercury. This ex- 150 haustion of the envelope may be attained by the employment of any suitable means, as for example a Gaede or condensation pump, now well known to the art. Besides evacuating the interior of the envelope per se, the materialsinside the envelope should be suitably treated to remove therefrom occluded or otherwise retained gases.

Although I have described my invention with minute particularity this ,is not to be taken by way of limitaton, but by way of illustration and the invention is to be limited only by the prior art. i

What is claimed is: Y 1. A switch comprising a di-electric evacuated envelope having a plurality of re-entrant tubes and a plurality of lead-in conductors extending therewithin, one of said re-entrant tubes having a press, one of Asaid lead-in conductors sealed in saidpress, a plurality of electrodes, one of said electrodes connected to said lead-in conductors sealed to said press, means secured to'said conductor and engaging said re-entrant tube, having the press, to relieve the seal from at least a portion of the strain caused-by impact during operation of the switch, another electrode movable relative to said first mentioned electrode,

means associated with said movable electrode to guide the same during the travel thereof, said means being adjacent a wall of said electrode, a terminal exteriorly of the envelope for said movable electrode, a flexible cushioning and conducting means electrically connected to said movable electrode and to said terminal.

2. A switch comprising a di-electric evacuated -envelope having a plurality of re-entrantA tubes and aplurality of lead-in conductors extending therewithin, one of said re-entrant tubes having a press, one of said lead-in conductors sealed in said press, an electrode connected to said leadin conductor sealed to said press, means secured to said conductor and frictionally engaging said re-entrant tube. having the press, to relieve said seal from lat least a portion of the strain caused by impact during the operation of the switch, a second electrode relatively movable with respect to said ilrst mentionedl electrode, another re-entrant tube associated with said movable electrode to guide the same during the travel thereof, a terminal exteriorly of said envelope for said lmovable electrode, and a flexible cushioning and conducting means electrically connected to said movable electrode and to said terminal and located within the envelope.

3. A switch comprising a di-electric evacuated envelope having a re-entrant tube and a plurality of lead-in conductors extending therewithin, said re-entrant tube having a press, a lead-in conductor sealed in said press, an electrode connected to said lead-in conductor sealed to said press, means secured to said conductor to relieve the seal from at least a portion of the strain caused by impact during the operation of the switch, another electrode movable relative to said ilrst mentioned electrode and including a body of magnetic material, means associated with said movable electrode to guide the same during the a plurality of lead-in conductors extending within said tubular arms, one of said re-entrant tubes having a press, one of said lead-in conductors sealed in said press, an electrode connected to said lead-in conductor sealed to said press and having the contact portion thereof located within said bulbous mid-portion, means secured to said conductor to relieve said seal from at least a portion of the strain caused by impact during the operation of `the switch, another electrode movable relative to said first mentioned electrode and having its contact portion also located within the bulbous mid-portion of the envelope, means associated with said movable electrode to guide the same during the travel thereof, saidmeans being adjacent a wall of said movable electrode, a terminal exteriorly of the envelope for said movable electrode, a flexible cushioning and conducting means electrically connected to said movable electrode and to said terminal, said movable electrode including a member of magnetic material, and means outside of the envelope for magnetizing said magnetic. material.

5. A switch comprising a di-electric evacuated envelope having a re-entrant tube and a. plurality of lead-in conductors extending therewithin, one of said re-entrant tubes having a press, one of said lead-in conductors sealed in said press, one of saidelectrodes connected to said lead-in conductor sealed to said press, meanssecured to said conductor and engaging said re-entrant tube to relieve the seal from at least a portion of the strain caused by impact during operation of the switch, another electrode movable relative to said first mentioned electrode, said movable electrode including a hollow shell supporting a body of magnetic material, means associated with said movable electrodevto'guide'the same during the travel thereof, said means being adjacent a wall of said movable electrode, a terminal exteriorly of the envelope for said movableelectrode, a flexible cushioning and conducting vmeans electrically connectedto said movable electrode and to said terminal and means outside of the envelope for magnetizing said magnetic member to actuate said movable electrode. 4

6. A switch comprising a di-electric evacuated envelope having a re-entrant tube and a plurality of lead-in conductors extending therewithin, said re-entrant tube having a press, one of said lead-in conductors sealed to said press, an electrode connected to said lead-in conductors sealed to said press, means secured to said conductor and engaging said re-.entrant tube to relieve the seal from at least a portion of the strain caused by impact during operation of the switch, said electrode having a contact surface area substantially free from points or sharp lines to evacuate cold electron emission therefrom during the operation of the switch, another electrode movable relatively to said iirst mentioned electrode, and consisting of a magnetic body secured to a hollow shell, tubular means associated with said travel thereof, a wall of vsaid tubular means being closely adjacent a wall of said movable electrode, a terminal exteriorly of the envelope for said movable electrode, a flexible cushioning and conducting means electrically connected to said' movable electrode and to said terminal, and means exteriorly of said envelope for magnetizing said magnetic body to actuate said movable electrode.

7. A switch comprising a di-electric envelope having a re-entrant tube and a plurality of lead- 'movable electrode to guide the same during the in conductors' therewithin, said reen trant tube having a press, one oi' said lead-in conductors sealed in said press, an electrode connected to said lead-in conductor sealed to said press, the contact portion o! said electrode being ared outwardly to' provide a contact surface substantially free from sharp' points and lines to prevent the establishment of relatively high potential gradients along this surface during certain periods of the operation of the switch, means/ secured to said conductor and engaging said reentrant tube to relieve the seal from at least a portion oi the strain caused by impact during the operation of the switch, another electrode movable relative to said ilrst mentioned electrode and being a hollow shell with a cup-shaped lcontact portion and carryng a magnetic body, means associated with said movable electrode to Aguide the same during the travel thereof, said means being adjacent a wall oi said movable electrode, a terminal exteriorly of the envelope for said movablev electrode, a ilexible cushioning and conducting means electrically connected to said movable electrode and to said terminal.

8. A switch comprising a di-electric evacuated envelope including a bulbous mid-portion and a plurality of diametrically opposed tubular arms, a plurality oi re-entrant tubes and a plurality of lead-in conductors in said tubulai arms, one of said re-entrant tubes having a press. one of said lead-,in conductors sealed in said.

having the press, to relieve said seal from at least a portion of the strain caused by impact during the operation ofthe switch, another electrode movable with respect to said flrst mentioned electrode and having a wall thereof adjacent a wall of another re-entrant tube to guide the same during the travel thereof, said movable electrode being a hollow shell supporting a body o! magnetic material, a terminal exteriorly of the envelope for said movable electrode, the contact areas of said electrodes located in the bulbous mid-portion of the envelope, a ilexible cushioning and conducting means electrically connected to said movable electrode and to said terminal.

CLAYTON TRIDLE ULREY.

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